Animal feed and methods for reducing ammonia and phosphorus levels in manure

ABSTRACT

An animal feed is provided that employs a substantially indigestible cation exchanger capable of binding ammonium cations and an acidogenic substance to acidify an animal&#39;s manure and thereby create ammonium cations that can be bound by the cation exchanger. The animal feed reduces ammonia emissions from manure produced by animals fed the animal feed compared to the emissions obtained from manure when an acidogenic substance is fed alone and compared to the emissions obtained from manure when a cation exchange capacity material is fed alone. According to another aspect of the present invention, a method of lowering ammonia emissions from manure is provided. The present invention also provides a method for reducing soluble phosphorus levels in manure and a method for reducing total phosphorus levels in manure. In a further aspect of the present invention, a method is provided that yields manure that may be used alone or in concert with other materials to act as a fertilizer having advantageous ecological properties. Another aspect of the present invention provides a method for reducing insect populations associated with manure.

This application is a continuation of U.S. patent application Ser. No.10/868,070 filed Jun. 15, 2004, which claims the benefit of U.S. patentapplication Ser. No. 60/499,988 filed on Sep. 4, 2003, U.S. patentapplication Ser. No. 60/541,500 filed on Feb. 3, 2004, and U.S. patentapplication Ser. No. 60/541,622 filed on Feb. 4, 2004, all of which arehereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates generally to animal feeds and methods of feedinganimals that produce more environmentally benign waste products.

BACKGROUND

The number one complaint filed with both state and federal environmentalagencies against animal producers involves odors. What is true foranimal producers in general is also true for poultry producers.Controlling odors associated with poultry manure is a continuing problemfor poultry and egg producers. Aerosol ammonia is one of the primarycauses of nuisance odors associated with confined animal feedingoperations. Since aerosol ammonia comprises a large portion of the odorassociated with poultry litter, measures to control odor at poultryoperations should incorporate strategies to reduce ammoniavolatilization. In addition to ammonia's role as a component in nuisanceodors, high levels of gaseous ammonia adversely affects animal healthand the safety of people working in these environments.

Aerosol ammonia levels in hen houses with shallow pits and monthlymanure removal have been measured to be in the range of 46 parts permillion (ppm). Similarly, the levels of aerosol ammonia in hen houseswith deep pits (manure-drying pits where manure is removed annually)have been measured to be in the 46 ppm range. Gaseous ammonia levels areespecially high in winter, when hen house ventilation is restricted toconserve heat. During cold weather, gaseous ammonia levels in hen housesoften exceed the 46 ppm range.

Poultry, for example, chickens and turkeys, continuously exposed to 20(ppm) ammonia vapors exhibit significant respiratory tract damage afteronly six weeks. Chicks exposed to 20 ppm ammonia for 72 hours are muchmore susceptible to Newcastle Disease than chicks reared in ammonia-freeenvironments. A high level of ammonia in the environment of layingchicken hens is also known to reduce egg production. For a more thoroughdiscussion of the effect of high levels of gaseous ammonia on animalhealth and production, the reader is directed to the following articlesthat are incorporated by reference herein in their entirety. See: AvianDis. 8:369-379, 1964; Deaton et al. Poultry Sci., 63:384-385, 1984;McQuitty et al. Canadian Agricultural Engineering 27:13-19; Strombaughet al. J. Anim. Sci. 28:844, 1969. Similarly, high ammonia levelscorrelate with a reduction in the amount of animal feed converted toanimal body mass and reduced weight gain in hogs.

In addition to ammonia's adverse effects on animal health, exposure tohigh levels of aerosol ammonia also adversely impacts human health. Forexample, exposure to aerosol ammonia concentrations in the range of 25parts per million (ppm) produces discomfort in workers, and even briefexposures (<5 minutes) to ammonia can cause nasal irritation anddryness. In recognition of the ill effects of aerosol ammonia on humanhealth, both the National Institute for Occupational Safety and Health(NIOSH) and the Occupational Safety and Health Administration (OSHA)identify ammonia as a health hazard. Currently NIOSH rules set thepermissible exposure level (PEL) for ammonia over an 8-hour period at 25ppm. OSHA rules set a PEL, over an 8-hour period, at 50 ppm. OSHA alsorecognizes that an aerosol ammonia concentration of 300 ppm ammonia isimmediately dangerous to life or health (IDLH). 29 C.F.R. 1910.120(2003) defines IDLH as “[a]n atmospheric concentration of any toxic,corrosive or asphyxiant substance that poses an immediate threat to lifeor would cause irreversible or delayed adverse health effects or wouldinterfere with an individual's ability to escape from a dangerousatmosphere.”

In addition to the problems associated with aerosol ammonia in animalmanure, manure often times comprises high concentrations ofwater-soluble forms of phosphorus. High concentrations of phosphorus cancause environmental problems, especially if the phosphorus finds its wayinto surface water sources or shallow aquifers. Manures from monogastricanimals such as hogs and poultry are especially high in phosphorus dueto the inability of monogastric animals to digest phytic acid, aphosphorus-rich compound commonly found in animal feeds. The presence ofhigh levels of soluble phosphates in manure is especially problematicwhen manure is disposed of by spreading it over fields or when feedlotsare located near watersheds or above shallow aquifers. Examples ofenvironmental damage caused by manures high in soluble phosphatesinclude fish kills and bacterial or algal blooms exacerbated by theintroduction of phosphates from manure into surface waters.

While plants require phosphorus in order to grow, excess levels ofphosphorus can stunt plant growth and in some cases cause plant death.This is especially problematic, as one common means of disposing ofmanure is to use it to fertilize plants. Accordingly, phosphorus must beprovided to plants in amounts conducive to and not detrimental to plantgrowth and development. When phosphates are provided to plants inamounts that exceed the plants' ability to absorb these compounds,excess phosphates accumulate in the soil or find their way into thewatershed.

One widely used measure of fertilizer efficacy is the fertilizer'sNitrogen to Phosphate ratio (N:P ratio). For most plants, a N:P ratio inthe 5.8:1 range is acceptable. When the N:P ratio is substantially lowerthan 5.8:1, a compound may provide more phosphate than plants canreadily absorb while providing less nitrogen than the plants require foroptimal growth. Off-gassing of ammonia lowers the nitrogen content inmanure, thereby decreasing the nitrogen/phosphorus ratio in the manure.Especially if manure is already high in phosphorus, as ammonia isoff-gassed the N:P ratio may become so low that the manure must undergocostly processing before it can be used as a fertilizer.

Clearly then, there is a need for methods to produce a manure thatexhibits low levels of gaseous ammonia and has a N:P ratio in a rangesuitable for its ready use as a fertilizer.

SUMMARY OF THE INVENTION

One embodiment of the invention is an animal feed ration that helps toreduce the level of volatile ammonia in manure produced by an animal fedthe ration. One embodiment comprises a cation exchanger capable ofbinding ammonium cations and an acidogenic compound, wherein theacidogenic compound lowers the pH of the manure produced by an animalfed the animal feed such that ammonia in the manure is protonated toproduce ammonium cations. A variation of this embodiment includes alevel of crude protein reduced relative to a conventional feed. In onevariation of this embodiment, the reduced crude protein feed issupplemented with at least one at least partially purified amino acid.

Another embodiment is a method of reducing the level of ammonia aerosolfrom manure, comprising the steps of providing an animal feed includinga cation exchanger capable of binding ammonium cations and an acidogeniccompound and feeding the animal feed to an animal. The acidogeniccompound is present in one variation of this embodiment such that theinitial pH of the animals' excreta is reduced to a pH of ≦9.3. Inanother variation of this embodiment, the pH is reduced to <7.

Still another embodiment is a method of producing manure comprising thesteps of providing a feed ration including a cation exchanger capable ofbinding ammonium cations and an acidogenic compound capable of reducingthe pH of the manure and feeding the feed ration to an animal. At leasta portion of the ammonia in manure produced by animals fed these rationsis protonated to form ammonium cations that bind to the cationexchanger.

Another embodiment is a fertilizer comprising manure produced by ananimal fed a ration including a cation exchanger capable of bindingammonium cations and an acidogenic compound that reduces the pH of themanure.

Another embodiment is a method for controlling the number of insectsassociated with manure. The method comprises the steps of providing afeed ration including a cation exchanger capable of binding ammoniumcations and an acidogenic compound capable of reducing the initial pH ofthe manure produced by an animal fed the feed ration and feeding thefeed ration to an animal. At least a portion of the ammonia in themanure is protonated to form ammonium cations that bind to the cationexchanger.

Another embodiment comprises an animal feed including a cation exchangercapable of binding ammonium cations and an acidogenic compound, whereinthe acidogenic compound lowers the pH of the manure produced by ananimal fed the animal feed such that ammonia in the manure is protonatedto produce ammonium cations. In this embodiment, the manure has asubstantially lower level of aerosol ammonia than manure produced by ananimal fed a conventional industry standard diet.

A further embodiment of the present invention comprises a method ofreducing the level of ammonia aerosol from manure. The method comprisesthe steps of providing an animal feed including a cation exchangercapable of binding ammonium cations and an acidogenic compound capableof reducing the pH of manure produced by an animal fed the animal feedand feeding the animal feed to an animal. At least a portion of theammonia in the manure is protonated to form ammonium cations that bindto the cation exchanger. In this embodiment, the animal feed reduces thepH of the manure produced by the animal fed the animal feed compared toa pH expected from a manure produced by the animal when it is fed aconventional industry standard animal feed. The animal feed in thisembodiment also increases the amount of ammonium cations protonated fromthe ammonia in the manure produced by the animal fed the animal feedcompared to an amount of ammonium cations protonated from ammonia in amanure produced by the animal when it is fed a conventional industrystandard diet.

Yet another embodiment is a method for reducing the level of solublephosphorus in manure comprising the steps of providing an animal feedincluding a cation exchanger capable of binding ammonium cations, anexchangeable phosphate reactive metal associated with the cationexchanger, and an acidogenic compound and feeding the animal feed to ananimal. The animal manure produced by this method has lower levels ofsoluble phosphorus than manure produced by the animal fed theconventional industry-standard animal feed. In still another embodiment,the phosphate reducing feed further includes compounds that reduce theamount of phosphate in the manure. Compounds such as phytase reduce theamount of phosphate in the manure by making more phosphate bioavailablefor incorporation into animal tissue and products.

Another embodiment is a fertilizer comprising manure produced by ananimal fed a ration including a cation exchanger capable of bindingammonium cations and an acidogenic compound. The acidogenic compound ispresent in the ration such that at least a portion of the ammonia in themanure is protonated to form ammonium cations. Fertilizer made frommanure produced by the animal fed the inventive ration has a morefavorable (higher) N:P ratio than similarly produced fertilizer madeusing manure produced by animals fed a conventional industry standarddiet.

Still another embodiment is a method for controlling the number ofinsects associated with manure comprising the steps of providing a feedration including a cation exchanger capable of binding ammonium cationsand an acidogenic compound and feeding the feed ration to an animal. Theacidogenic compound reduces the pH of manure produced by an animal fedthe animal feed the ration such that at least a portion of the ammoniain the manure is protonated to produce ammonium cations. The manureproduced by the animal fed the feed ration reduces the number of insectsassociated with the manure from a number of insects associated with amanure produced by the animal fed a conventional industry-standard feedration.

In still another embodiment, an animal ration is amended to produce afirst manure produced by an animal fed said amended animal ration, saidfirst manure having a high N:P ratio relative to a second manureproduced by said animal fed a conventional industry standard diet. Theinventive amended animal ration includes means for lowering a totalamount of crude protein in the amended animal ration relative to a totalamount of crude protein contained in the conventional industry standarddiet; means for lowering a volatile ammonia content of the first manurerelative to a volatile ammonia content of the second manure; means forincreasing an amount of bio-available phosphorus in the amended animalration relative to an amount of bio-available phosphorus contained inthe conventional industry standard diet; and means for reducing a totalamount of phosphorus in the amended animal ration relative to a totalamount of phosphorus contained in the conventional industry standarddiet.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph of ammonia emissions measured from hen manure samples.These data were collected over a 7-day period and are reported in unitsof parts per million (ppm). Briefly, manure samples were taken fromchicken hens fed one of the following three feed rations: a.) a controlfeed ration identical to an industry standard feed, wherein the controlration included 18.8% crude protein by weight and 4.2% calcium byweight; b.) a feed ration similar to the control feed ration butsupplemented with calcium sulfate (gypsum) such that gypsum provided 45%of the calcium in the feed; and c.) a feed ration similar to the controlfeed ration supplemented with 2% by weight zeolite.

FIG. 2 is a graph of ammonia emissions from chicken hen manure measuredover a 7-day period. The ammonia emissions are reported in units ofparts per million (ppm) ammonia. Briefly, manure samples were collectedfrom hens fed one of the following three feed rations: a.) a controlration including 18.8% crude protein by weight and 4.2% calcium byweight; b.) a feed ration similar to the control feed rationsupplemented with about 2% by weight zeolite and gypsum, the amount ofgypsum added to the ration was sufficient to provide about 45% of thecalcium in the ration; and c.) a feed ration similar to the controlration but having only 15.0% by weight crude protein. This ration wassupplemented with lysine such that lysine comprised 0.98% by weight ofthe feed, the ration also included, 2% by weight zeolite, and gypsum.The amount of gypsum added to trial c was sufficient to provide about45% of the calcium in the feed.

FIG. 3 is a graph of ammonia emissions in parts per million (ppm),measured over a 7-day period, from chicken hens fed a) a control diet offeed containing 18.8% crude protein by weight and 4.2% calcium byweight; b) the control diet supplemented with gypsum, which was added inan amount sufficient that the gypsum was the source of 45% of thedietary calcium; c) the control diet supplemented with zeolite, whenzeolite comprised 2% by weight of the feed; d) the control dietsupplemented with gypsum and zeolite when gypsum was the source of 45%of the dietary calcium and zeolite comprised about 2% by weight of thefeed; and e) a reduced (relative to the control diet) crude protein dietwherein the calcium content remained at 4.2% by weight, and crudeprotein comprised 15.0% by weight of the feed. Additional lysine wasadded to the ration used in 5 e such that lysine comprised 0.98% byweight of the feed. The feed used in FIG. 5 e also included gypsum andzeolite. Gypsum was the source of about 45% of the dietary calcium inthe feed, and zeolite comprised about 2% by weight of the feed.

FIG. 4 is a graph of ammonia emissions in parts per million (ppm),measured over a 7-day period, from chicken hens fed a) a control diet offeed when crude protein comprised 14.8% by weight of the feed andcalcium comprised 4.2% by weight of the feed; b) a diet when crudeprotein comprised 15.3% by weight of the feed, calcium comprised 4.2% byweight of the feed, gypsum was the source of 25% of the dietary calcium,and zeolite comprised 1.25% by weight of the feed; c) a diet comprisinga reduced (relative to the control diet) amount of crude protein whencrude protein comprised 14.3% by weight of the feed, with additionallysine added so that lysine comprised 0.84% by weight of the feed,calcium comprised 4.2% by weight of the feed, gypsum was the source of35% of the dietary calcium, and zeolite comprised 1.25% by weight of thefeed.

FIG. 5 is a graph of fly card data collected in hen houses plotted as afunction of weeks on which egg laying hens were fed either standard oramended rations. These data illustrate a significant reduction in thenumber of flies associated with hens fed amended rations comprisingzeolite and an acidogenic compound versus hens fed the industry standard(control) rations. The reduction in flies was first observed during week4 of the study and continued through the end of the study (weeksixteen).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the preferred embodimentsthereof, and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations, modifications, andfurther applications of the principles of the invention beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

A number of explanations and experiments are provided by way ofexplanation and not limitation. No theory of how the invention operatesis to be considered limiting whether proffered by virtue of description,comparison, or example.

In most cases, the preponderance of nitrogen present in excreta is inthe form of urea. Urea present in the urine is a source of the largeamount of gaseous ammonia emitted shortly after excretion. Urea inmanure is converted to ammonia by urease, an enzyme present in excretathat hydrolyzes urea into ammonia. A set of chemical equations detailingthe conversion of urea to ammonia is as follows:CO(NH₂)₂+2H₂O→+2NH₄ ⁺+CO₃ ²⁻  (1)CO₃ ²⁻+H₂O→HCO₃ ⁻+OH⁻NH₄ ⁺+OH⁻→NH₃↑+H₂O

As indicated previously, the enzyme urease catalyzes reaction (1). Underacidic conditions, ammonia is readily protonated to form ammoniumcations, a less volatile positively charged molecule. Ammonium has apK_(a) of about 9.34. Once the pH of the manure becomes high enough,free ammonium will deprotonate to form ammonia, which is more likely tooff-gas than is the ammonium cation. Low pH favors ammonium formation,so the presence of acidogenic compounds in manure favors the conversionof ammonia to ammonium. However, as illustrated by the above set ofchemical equations, the pH of manure tends to increase over time as ureaand other nitrogen containing compounds are converted into ammonia andhydroxyl ions (OH-) are released. The release of hydroxyl anions tendsto increase the pH of the manure.

Those of skill in the art will recognize that nitrogen present inundigested amino acids in the manure may provide a source of additionalaerosol ammonia emissions. Additional volatile ammonia can form inmanure as proteins, amino acids, and other nitrogen-bearing molecules inmanure are broken down by either microbial or chemical action. Ingeneral, degradation of non-urea nitrogen sources, such as amino acidsfound in proteins, does not generate large amounts of ammonia at anygiven time; instead, such degradation facilitates a slow, gradualrelease of nitrogen.

Reducing the pH of manure can reduce ammonia volatilization, regardlessof its immediate source from manure. Ammonium is a weak acid with apK_(a) of about 9.34. It behaves more like an alkali earth metal thandoes ammonia. The pH of manure can be reduced by adding acidogeniccompounds to an animal's feed rations. In one embodiment of theinvention, acidogenic compounds are compounds that are converted intopH-reducing compounds in an animal's digestive tract. When the pH ofmanure falls to below the pK_(a), the equilibrium between unchargedvolatile ammonia (NH₃) and the less volatile cationic form ammonium (NH₄⁺) shifts in favor of the production of ammonium cations.

Some acidogenic compounds not only lower the pH of manure they reactwith ammonium cations to form stable compounds that are not readilyconverted back to ammonia even as the pH of the milieu increases.Acidogenic compounds that react with ammonium cations to form stablecompounds include, but are not limited to, aluminum sulfate (alum),sulfuric acid, and sodium bisulfite. The formation of compounds such asammonium sulfate reduces the concentration of free ammonium cations inthe manure, thereby further shifting the equilibrium between ammoniumand ammonia toward the formation of ammonium.

As used herein, the term manure refers to all forms of animal excretaincluding feces, urine, and uric acid as well as excreta mixed withbinders, fillers, absorbents, and the like. Examples of such absorbentsinclude but are not limited to straw, hay, processed paper products,fertilizer components, and the like.

As used herein, the term urine refers to all forms of nitrogen-richwaste processed by the kidneys of an animal. Manure includes, forexample, liquids produced by animals such as pig, sheep, cows, etc.; andsemi-solid forms as are commonly produced by fowl, including, forexample, chickens, ducks, geese, and the like.

As used herein, an acidogenic compound is a compound that can be addedto an animal's feed to reduce at least transiently the pH of theanimal's manure. One group of acidogenic compounds includes compoundsthat are digested by an animal to form products that reduce the pH ofmanure produced by the animal. Still another group of acidogeniccompounds substantially survives digestion, and they themselves can befound in the animal's manure acting to reduce the pH of manure. Eithertype or a combination of both types of acidogenic compounds can be usedto practice the invention.

As used herein, the ratio of Nitrogen to Phosphorus may be expressed aseither N:P or N/P. Also, as used herein, the term “conventional industrystandard diet” and the term “industry standard feed” have substantiallysimilar meanings. These terms refer to animal feeds that generally donot include appreciable amounts of acidogenic compounds or cationexchange materials that are excreted and find their way into manureproduced by the animals. Acidogenic compounds and cation exchangers maybe added to animal feed in order to reduce the level of ammonia emittedfrom manure produced by animals fed such diets.

For example, one such conventional industry standard diet is the onerecommend by HY-LINE International for W-36 egg producing hens. For afurther discussion of this conventional industry standard diet, thereader is directed to “Hy-Line Variety Commercial Management Guide2003-2004” published by Hy-Line International, West Des Moines, Iowa, U.S. A. and available online at www.hyline.com, which document isincorporated herein by reference in its entirety. Those of ordinaryskill in the art will recognize that the conventional industry standarddiet varies from species to species, and even within a given species mayvary depending upon factors such as variety, age, health, and theutility of the animal.

The reduction in manure pH achieved by supplementing an animal's feedwith an acidogenic compound is temporary, generally lasting only betweenone and three days. Lysine, cellulose, benzoic acid or salts of benzoicacid, or ammonium salts of carboxylic acids are all examples ofacidogenic substances. Additional examples of acidogenic compounds thatmay be added, with varying degrees of success, to animal feed to reducethe pH of manure include salts of mineral acids, such as alkaline earthmetal salts of mineral acids. Examples of the latter group of acidogenicsubstances include, for example, calcium chloride and calcium sulfate(gypsum).

Additionally, certain materials, when added to manure, may inhibit theactivity of the enzyme uricase. Uricase acts in concert with otherenzymes to convert uric acid in poultry manure to urea. Urea is thenconverted into ammonia by the enzyme urease. The optimal pH for uricaseactivity is generally around 9.2 SU. Uricase activity drops off below pH7 SU and above 10 SU. Reducing the pH of manure below 7 inhibits uricaseactivity and decreases the amount of ammonia associated with the manure.

Compounds containing zinc, copper, manganese, and magnesium are known tohave an inhibitory effect on uricase activity. These metals inhibituricase activity irrespective of pH. These effect inhibitory effects oflow pH and specific metals may be combined by feeding animals mineralacids made from metals that inhibit uricase activity. However, directlyfeeding animals high levels of salts of such metals may have adetrimental effect on animal health. For this reason, these compoundsare often fed as an electrolyte, or as an acidogenic substance fed inconcert with other less toxic acidogenic substances.

It may be advantageous to add acidogenic compounds to animal feeds thatprovide more than just a reduction in pH or the capacity to form stablecompounds with ammonia or ammonium cations. For example, acidogeniccompounds such as calcium sulfate and calcium chloride provide theanimal with a source of calcium and an anion (either sulfate orchloride) and also provide anions that react with ammonium cations toform stable nitrogen rich complexes. The amino acid lysine is anotherexample of a compound that can have an advantageous impact on bothanimal health and ammonia reduction. If an animal is fed lysineincluding a counter-anion, when the lysine is metabolized the counteranion may survive the digestion process and combine with ammoniumcations in the manure.

As mentioned earlier, a portion of the ammonia found in manure comesfrom the breakdown of amino acids in the manure. The major source ofamino acids in animal manure is undigested or only partially digestedproteins and peptides originally found in the animal's feed. “Crudeprotein” is a general term used to describe proteins comprising a widerange of amino acids added to or at least found in animal feeds. In partbecause animals have the capacity to biosynthesize some amino acids butnot others, an animal feed may be deficient in some amino acids butharbor an excess of other amino acids.

Most animals require minimum amounts of specific amino acids in theirdiets in order to thrive. Amino acids that must be provided to an animalin its diet include amino acids that the animal cannot biosynthesize.These amino acids are referred to as essential amino acids. Similarly,some animals will grow more efficiently if they are provided a diet richin certain amino acids than if they are fed a diet having sub-optimalamounts of these amino acids. Limiting amino acids are amino acidspresent in an animal feed at such low levels that they limit theproductivity of the animal fed that diet. In part because of the unequaldistribution of amino acids in various crude protein sources, a crudeprotein source may have an excess of some amino acids while beingdeficient in other amino acids.

The list of essential amino acids and amino acids that are difficult tobiosynthesize varies from species to species but often includes, forexample, lysine, methionine, threonine, and tryptophan. These are alsoprimary amino acids that often act as limiting factors on the metabolismof a laying hen.

When excess amino acids are excreted, they break down and contribute tothe amount of volatile ammonia in the excrement. Given that proteins inmanure contribute to the amount of ammonia produced by the manure,reducing the levels of crude protein fed to an animal can help to reducethe amount of volatile ammonia in an animal's manure.

It is one aspect of the invention to reduce the level of volatileammonia in manure by reducing the amount of crude protein in an animal'sfeed rations. While this approach clearly helps to reduce the amount ofammonia in an animal's manure, care must be taken with this approach asimbalances in amino acid content are magnified when crude protein levelsare reduced. In order to simultaneously reduce the level of excess aminoacids in an animal's feed while at the same time providing an optimallevel of all amino acids, animal feed can be supplemented with specific,otherwise limiting, amino acids. By significantly reducing total crudeprotein levels and adding back a required amount of one or all of theselimiting amino acids, it is possible to reduce the total amount of aminoacids excreted by hens without reducing the hen's metabolism. Fewerexcreted amino acids result in less nitrogen (and less ammonia) in themanure.

In still another aspect of the invention, volatile ammonia levels inmanure are reduced by adding compounds to an animal's feed ration thatare converted to cationic compounds which react with ammonium cations toform stable compounds. Compounds that can react with ammonium cations toform stable compounds include but are not limited to sulfate. Sulfateanions readily react with ammonium cations to form ammonium sulfate.Ammonium sulfate is stable at alkaline pH. Accordingly, nitrogensequestered in the form of ammonium sulfate is not free to form volatileammonia even as the pH of the manure drifts upwards.

One particularly good source of sulfate ions for the practice of theinvention is gypsum (calcium sulfate). Gypsum is inexpensive, and inaddition to providing a source of sulfate ions for the control ofammonia levels in manure, it provides the animal with a requiredelement, calcium.

Simply feeding an animal a ration rich in gypsum may not be enough tosignificantly reduce the amount of volatile ammonia in the animal'smanure. Referring now to Table 1 and FIGS. 1 and 3, the amount ofammonia off-gassed from manure produced by an animal fed rationssupplemented with gypsum only increased 24 hours after the manure wasproduced relative to the ammonia off-gassed from manure produced by ananimal fed a control ration. Over the period of one week, the levels ofammonia emitted from manures produced by hens fed rations supplementedwith gypsum were only 15% lower than the levels of ammonia emitted frommanures produced by hens fed control rations.

In another aspect of the invention, an animal is fed a ration comprisingcompounds that effectively bind ammonium cations. One particularlyattractive method is to feed the animal a cation exchanger thatsubstantially retains its affinity for cations even after it has passedthrough the animal's digestive tract. Materials with a high cationaffinity include compounds with a high cation exchange capacity. Oneclass of compounds with high cation exchange capacities that areparticularly useful for the practice of the invention is the class ofzeolites. Zeolites have a high capacity to bind cations such as ammoniumions, and zeolites generally can pass through the gut of most animalswith their affinity for cations substantially unchanged.

Referring still to Table 1 and FIGS. 1 and 3, merely feeding an animalrations supplemented with zeolite alone does not significantly reducethe level of ammonia off-gassed from manure produced by the animal. Oneplausible explanation for these data, presented by way of illustrationand not limitation, is that the manure produced by hens fed a dietsupplemented with zeolite, but not an acidogenic compound, is alkaline.Highly alkaline conditions favor the formation of ammonia, and ammoniadoes not effectively bind to zeolite.

It is one aspect of the invention to feed animals a ration comprisingboth one or more cation exchangers such as zeolite and one or moreacidogenic compounds. Acidogenic compounds in the animal's manure willreduce the pH of the manure, thereby promoting the protonation ofammonia to form ammonium, which can then bind to zeolite.

Referring again to Table 1 and FIGS. 2 and 3, hens fed rationscomprising both gypsum and zeolite produced manure that off-gassedsubstantially less ammonia than manure produced by hens fed rationsformulated with neither zeolite or gypsum (or with only one of thesecompounds). Again by way of explanation and not limitation, it is likelythat the sulfate in the manure (from gypsum) reduced the pH of themanure and reacted with some of the ammonia to form ammonium sulfate. Atthe same time, ammonium cations that did not react with the sulfateanions bound to zeolite in the manure. Ammonium cations bound to zeoliteare not readily deprotonated even at alkaline pH, and therefore theoverall level of ammonia off-gassed decreased over the 1-week period forwhich data was collected.

In yet another aspect of the invention, the level of volatile ammonia inanimal manure is reduced by feeding an animal a ration comprisingreduced levels of crude protein and supplements of zeolite and calciumsulfate (gypsum). Referring still to Table 1 and FIGS. 2 and 3, theamount of volatile ammonia from hen manure was further reduced byreducing the amount of crude protein in the animals' rations. Manureswith the lowest level of ammonia were those produced by hens fed reducedcrude protein diets wherein the feed was supplemented with both zeoliteand gypsum.

Poultry excrement is rich in uric acid. Accordingly, poultry manure isessentially a semi-solid. In other animals, for example, hogs, theanimal's excrement is comprised of a semi-solid (feces) and a liquid(urine). If an animal's excrement contains urine in a liquid form, thenit can be physically separated from the animal's feces.

Sequestering of liquid urine and semi-solid feces is most readilyaccomplished when the animals are housed in a controlled environment.Because a large percentage of the urea is found in liquid urine, it isadvantageous to collect the urine separate from the remainder of theanimal's excreta. When practical, separating urine from feces helps tocontrol the release of ammonia from the manure. However, even whenmanure and feces are separated, degradation of nitrogen rich compoundsin the feces may still result in the release of ammonia.

Yet another aspect of the present invention provides a method forlowering the amount of ammonia off-gassed from animal excrementseparated into liquid and semi-solid components. Physically separatingfeces and urine decreases the rate at which ammonia is formed andoff-gassed from the feces. Absent the hydroxyl ions formed primarily bythe urea-/urease-catalyzed reaction in the urine, the pH of feces doesnot rise as quickly as when urine is present. The tendency toward alower pH helps to reduce the rate of ammonia production. When compoundsthat reduce the pH of the animal's feces are present, the rate ofammonia production is further reduced. Ammonia off-gassing from fecesseparated from liquid urine is reduced still further when zeolite orsome other ammonium binding cation is present in the manure.

When it is impractical to separate an animal's feces and urine, as isthe case with poultry, the pH of the mixed manure can be reduced by theaddition of acidogenic compounds to the animal's diet. One or moreacidogenic compounds in the animal's feed ration is capable of loweringthe overall pH of the animal's manure, thereby increasing theconcentration of ammonium relative to ammonia in the manure. A feedcomprising both an acidogenic compound and a cation exchanger, such aszeolite, further reduces the level of ammonia off-gassed as zeoliteforms stable complexes with ammonium cations. However, the pH of mostmanures rises over time, thereby favoring the production of ammonia.Because the pH of manure tends to increase over time, one aspect of theinvention is to add one or more acidogenic compounds and zeolite to theanimal's feed ration. Ammonium cations formed under low pH conditionsare then trapped by the zeolite before they can deprotonate to ammoniaas the pH increases.

Urease is most active in the pH range between 6.5 SU and 7.0 SU. Thoseof ordinary skill will recognize that ammonium ions form when ammonia isprotonated and that a low pH strongly favors this reaction. Therefore,the presence of acidogenic compounds in an animal's feed that helps toreduce the pH of the animal's manure will reduce the amount of ammoniaoff-gassed from the animal's manure.

If zeolite is present in manure at the same time ammonium cations areformed, then the zeolite will bind the cations. However, once the pHbecomes alkaline, the equilibrium between ammonium and ammonia willfavor the formation of ammonia, which does not bind to zeolite. Theresult of experiments summarized in Table 1 and FIGS. 1 and 3demonstrate that this is the case. There is a marked increase in therates of ammonia emitted from manures formed by animals fed rationscomprising zeolites but no acidogenic compounds over the 24-48 hourperiod right after excretion.

One embodiment includes feeding fowl a feed comprising calcium, protein,and phosphorus levels consistent with the nutritional requirements ofbirds of that species, variety, and age. In this embodiment,nutritionally available phosphorus levels are supplemented by additionof phytase to the feed. Phytase converts phytic acid, a source ofphosphate that most birds cannot metabolize, into a bio-available formof phosphate. By adding phytase, the total amount of phosphate added tothe feed can be reduced.

If required, inorganic phosphate in the form of dicalcium phosphate isadded to the feed. For example, a feed ration may contain about 0.1%available phosphorus. Additional phosphorus may be present in the feedas phytic acid. The enzyme phytase can be added to the feed to increasethe amount of bioavailable phosphorus by an additional 0.1%. The addeddicalcium phosphate supplies the balance of the phosphorus that theanimals require without significantly contributing to the amount ofphosphate in the animal's manure.

The total amount of crude protein in the feed can be reduced compared tothe level of crude protein found in industry standard rations. Forexample, initial reductions in crude protein levels preferablyapproached 4% in the amended diet compared to a standard diet. Loweringtotal crude protein levels will result in lower levels of protein in themanure and therefore microorganisms and insects metabolize less ammoniainto volatile ammonia released into the atmosphere from protein in themanure. The actual amount of purified amino acids that needs to be addedback depends upon the level of the limiting amino acids in the feed andthe nutritional requirements of the animals.

As the birds age, they require less protein and phosphorus. Accordingly,the level of crude protein and phosphorus in the bird's diets can bereduced as the animals age. Those of ordinary skill in the art willrecognize that this is a standard practice for laying hens. Reducedcrude protein levels in feed may follow this trend as the bird ages aswell, but dietary levels of limiting amino acids must be met if birdhealth and performance are not to suffer. In the event that proteinslevels are reduced to the point when an amino acid becomes limiting,purified forms of the limiting amino acids are added back to crudeprotein-reduced feeds to insure bird health and performance.

In one embodiment, gypsum is substituted for limestone as a source of atleast some of the calcium the animals require. Gypsum contains a lowerweight percentage of calcium than limestone, and this factor is takeninto account when supplementing feed with gypsum to insure that theanimals receive an adequate amount of calcium. In one embodiment, theweight percentage of calcium derived from gypsum is approximately 23%,and the weight percentage of calcium derived from limestone isapproximately 38%. In another embodiment, gypsum accounts for 25% to 35%of the amount of supplemental calcium added to the animal's feed.

In one embodiment, zeolite is added to the feed such that it comprisesbetween about 1.25% to about 2% by weight of the ration. The zeoliteused to supplement the feed can be a naturally occurring clinoptilolitethat contains significant levels of exchangeable calcium and magnesium.

The ratios of gypsum substitution and zeolite addition may be varied, asmay the particle sizes of the gypsum and zeolite materials chosen. It iswell established that smaller particles dissolve in the gut faster thanlarger particles. Laying hens require a slow release of a sufficientlevel of dietary calcium in order to make effective use of it duringeggshell production. For this reason, pulverized limestone (smallparticle size) is considered a less effective dietary supplement thanlarger limestone particles.

The gypsum and zeolite materials chosen for addition to the rations maybe varied from the more preferred materials taught herein and stillachieve the unexpected results of the invention. By way of example, andnot of limitation, gypsum comes in hydrous and anhydrous forms and maybe obtained in a variety of size gradations.

It should also be noted that crude protein levels in the instant feedration may be varied. Feed so amended may require the addition ofvarious purified amino acids so that the ration will include the minimumamount of any specific amino acids necessary for animal health.

Zeolites come in many different types and size gradations, and thosechosen by the skilled practitioner for use in the present invention maybe naturally occurring or manmade and may be of any usable size.Zeolites used in the invention may be pre-loaded with certain usablecations or may have beneficial cations already present. Use of any of avariety of acidogenic substances and types of zeolite or other highcation exchange capacity materials may also be of utility to the skilledartisan in achieving the unexpected results of the present invention.One especially useful form of zeolite is zeolite loaded withdissociateable phosphate binding metal. Such phosphate binding metalsinclude, but are not limited to, magnesium and calcium.

Additionally, other animals besides hens may be fed suitable rationsaccording to the teachings of the present invention in order to achievethe goals of the invention. Those of skill in the art will recognize thedietary requirements of the other animal(s) chosen, and modifying thepreferred embodiments of the present invention to suit such otheranimal(s) needs will not require undue experimentation.

All animals require a bioavailable source of phosphorus; therefore, allnutritionally complete animal feeds must include a source ofbioavailable phosphorus. However, if animals are fed a diet too rich inphosphate, then they will excrete the excess phosphorus or, moreaccurately, compounds comprising phosphorus such as phosphates. Manurefrom animals fed excess phosphorus may be a rich source of water-solublephosphate. The disposal of animal manure with a high soluble phosphatecontent can be problematic, as soluble phosphates can contaminate bothsurface waters and aquifers.

Given the potential for environmental damage presented by manure high insoluble phosphate, reducing the phosphorus content of manure may be ofgreat environmental benefit. One way to reduce soluble phosphates inmanure is to add phosphorus-reactive metals such as iron, calcium,magnesium, and aluminum, to the subject animal's manure. One problemwith this approach is that overfeeding of some of these metals may bedetrimental to animal health. For example, ill effects of overfeedingiron, magnesium, and aluminum are known.

One aspect of the invention provides a method of reducing solublephosphate levels in animal manure by feeding phosphorus-reactive metalswithout compromising animal health. Animals are fed a ration comprisingzeolite that binds high levels of phosphorus-reactive metals. The animaldoes not take up phosphorus-reactive metals bound to zeolite until theyare released in exchange for another zeolite-binding cation. Feedinganimals a form of zeolite with a high natural level ofphosphorus-reactive metals (or is pre-loaded with such metals) has anunexpectedly beneficial impact on the level of soluble phosphate in theanimal's manure. Zeolite binding phosphorus-reactive metals, that candissociate from the zeolite especially in exchange for other cations,are an effective means of delivering phosphate reactive metals to themanure. Other cations in the manure, for example, ammonium cations, maydisplace the dissociatable phosphate reactive metal, which then reactswith excess phosphorus to form an insoluble complex.

Data summarized in Table 3 illustrate some of the beneficial effects offeeding animals rations comprising zeolite-binding phosphorus-reactivemetals and gypsum. An animal fed a ration comprising zeolite bindingmetals and gypsum produce manure with a lower level of soluble phosphatethan manures produced by an animal fed industry standard (control)rations.

In one aspect, the invention provides animal rations capable of reducingthe total amount of phosphates in an animal's manure. Many rations,especially rations rich in grains, contain phytic acid. This compound isa major phosphorus storage source in plants. Monogastric animals inparticular have difficulty digesting phytic acid. Adding phytase to afeed ration that includes phytic acid can increase the amount ofbioavailable phosphorus in the ration. Phytase is an enzyme thatcatalyzes the hydrolysis of phytic acid to inosital and phosphoric acid.As illustrated by the results summarized in Table 3, feeding amonogastric animal a feed comprising reduced levels of phosphate resultsin the production of manure with lower levels of soluble phosphates.

Phosphoric acid is more readily absorbed by monogastric animals than isphytic acid. Therefore, adding phytase to animal feeds comprising phyticacid elevates the level of bioavailable phosphorus in the feed. For amore complete discussion of phytase, the reader is directed to U.S. Pat.No. 6,548,282, which patent is incorporated by reference herein in itsentirety.

Experiment Experiment 1

In order to determine the efficacy of adding a high cation exchangecapacity material pre-loaded with phosphate-reactive metals andacidogenic substances to animal feed rations, a test flock of whiteleghorn hens (HyLine W-36) was prepared. The test flock was subdividedinto several units so that the effects of the various feed strategiescould be monitored and compared. One unit acted as a control. This unitwas fed a conventional industry standard diet, which initially comprised18.8% by weight of crude protein, 4.2% by weight of calcium, and 0.5% byweight of bioavailable phosphorus. The conventional industry standarddiet fed to the hens of this and the following examples as a controlration was substantially similar to the diet rations described in“Hy-Line Variety Commercial Management Guide 2003-2004” published byHy-Line International, West Des Moines, Iowa, U. S. A. and availableonline at www.hyline.com.

A second unit was fed a ration of similar characteristics, whichdiffered from the control unit in that gypsum was partially substitutedfor limestone such that 45% of the calcium supplement for the diet wasderived from gypsum. A third unit was fed a ration substantially similarto the control ration, differing from the control ration in that itcomprised a naturally occurring low-sodium clinoptilolite zeolite addedsuch that it comprised 2% by weight of the feed ration. The form ofzeolite used in ration 3 comprised a significant level of exchangeablephosphate-reactive calcium and magnesium. A fourth unit was fed a dietsubstantially similar to the control diet, differing in that itcomprised zeolite in the amount of 2% by weight, and gypsum waspartially substituted for limestone such that 45% of the supplementalcalcium was derived from gypsum.

The fifth unit was fed a ration comprising 2% by weight of zeolite andgypsum substituted for limestone such that 45% of the supplementalcalcium was derived from gypsum. However, this fifth ration had asignificantly reduced crude protein level, being reduced from 18.8% byweight as in the control diet, to 15.0% by weight. This diet alsocontained 0.5% bioavailable phosphorus. The ration of the fifth unit wasfurther amended with a purified form of the amino acid lysine such thatlysine comprised 0.98% by weight of the feed to avoid detrimentaleffects from not providing enough limiting amino acids to thrive. Allrations in the study were equivalent in terms of kilo-calories (kcals)per pound.

All rations comprising limestone added as a source of calcium includedgranular limestone having particle sizes ranging from just under ¼ inchin diameter down to a coarse dust. It is well settled that the speed ofcalcium uptake in hens is influenced by granulation size of the sourceof calcium. For laying hens, a slow, continual uptake is preferable;hence the calcium source is moderately coarse. Smaller granules woulddigest too quickly, and the excess calcium liberated would be excreted,rather than used by the bird for vital functions.

During the experiment, the number and quality of eggs produced by hensfed various rations were compared. Hens fed the amended rations showedsome initial improvement in production over hens fed control rations.Eggs produced by hens fed the gypsum-substituted rations (hens in thesecond unit) weighed slightly less than eggs produced by hens fed thecontrol ration.

In the second phase of the experiment, the approximate upper limit ofgypsum replacement for the second, fourth, and fifth units of hens wasmeasured. The amount of gypsum in the ration was increased and theamount of limestone in the ration was decreased such that 66% of thesupplemental calcium in the ration was derived from gypsum. Hens fedthis ratio produced slightly fewer eggs, and the eggs they did producehad a slight (but still acceptable) decrease in eggshell quality. In thenext experiment, gypsum was added to the ration such that gypsumcontributed 75% of the supplemental calcium in the ration. Hens fed thisration produced fewer eggs than hens fed the control ration, and theeggs they did produce had unacceptable shell quality.

In still another variation of the experiment, the amount of calciumderived from gypsum was reduced to 45% of the total amount of calciumfed to the animals. When gypsum was supplemented at this level, both eggshell quality and egg production figures returned to acceptable levels.Cumulative data collected over a 1 year period, including data from theperiod of very high gypsum supplementation, showed an approximate 4%increase in egg production from hens fed the amended rations relative tohens fed control feed rations. Eggs produced by hens fed thegypsum/zeolite-amended rations were also, on average, heavier than eggsproduced by hens fed the control ration. Hen mortality was similar inall groups.

The production increase and egg weight increase noted may be due tobetter living conditions for the test hens compared to hens in a normalproduction environment. The increases may also be attributable to a feedformulation that enables the hens to make more efficient use of thefeed, or the increases may be caused by a combination of factorsincluding the aforementioned reasons.

One conclusion of the aforementioned study is that white leghorn hens(HyLine W-36) should not be fed a diet in which greater than about 66%of the calcium is derived from gypsum. Still another conclusion is thatsuch hens should be fed a diet that derives 50% or less of its calciumfrom gypsum.

Experiment 2

Manure produced by hens fed a ration that included the optimal amount ofgypsum substituted for limestone was assayed less than 1 hourpost-excretion. This manure was immediately transported to a laboratory,where the manure from each unit was homogenized and a 25-gram aliquotplaced in a flask. The flask was supplied with air via an air pump. Theair passed across the manure and collected the ammonia emitted. Theammonia-laden air was then bubbled through an acid solution to capturethe ammonia. Every 24 hours, for a period of 7 days, the acid solutionwas changed out for fresh solution, and the samples were assayed todetermine their levels of ammonia. Data resulting from the initial labanalyses are illustrated in Table 1.

FIG. 1 illustrates the effect of supplementing chicken feed with zeolitein the absence of added acidogenic substances. Chickens fed rationssupplemented with zeolite alone did not produce manure that emitted lessammonia than manure from birds fed the control ration. A comparison withammonia emission levels collected in Table 1 indicates a 13% increase inammonia emission levels from manure produced by chickens fed feedcomprising zeolite compared with the ammonia emission levels from manureproduced by chickens fed the control ration.

Also illustrated in FIG. 1 is the effect of substituting gypsum forlimestone on ammonia emissions. By week two of the study, the amount ofammonia emitted from manure produced by hens fed gypsum was lower thanthe amount of ammonia emitted from manure produced by hens fed thecontrol diet. However, the buffered nature of the manure appears to takeover in the 24-48 hour period, and ammonia emission rates determined formanure collected even from hens fed a gypsum-rich diet increasedsignificantly. Still, comparison calculations collected in Table 1illustrate that over a 1-week period there was a 15% reduction inoverall ammonia emissions from manure from hens fed the experimentaldiet.

As FIG. 2 illustrates, when gypsum-substituted diets were augmented withzeolite, there was a significant and unexpected decrease in ammoniaemissions from manure collected from hens fed the amended feed comparedto manure collected from hens fed the control diet. Comparisoncalculations in Table 1 indicate that over a 1-week period, relative tothe manure from hens fed the control ration, there was a 47% reductionin the amount of ammonia emitted from manure produced by hens fed thegypsum plus zeolite diet, as compared to a 15% reduction observed inmanure collected from hens fed the gypsum-supplemented diet.

Referring again to Table 1, comparing the control diet with thegypsum/zeolite diet containing standard crude protein levels shows an85% reduction in ammonia emissions for the 0-24 hour period. The data inTable 1 for the 24-48 hour period comparing the same diets shows a 69%reduction in ammonia emissions.

Manure from hens fed the gypsum/zeolite-augmented ration showed a 38%lower level of ammonia emissions in the first 24-hour period and 59%lower ammonia emissions in the 24-48 hour period than manure collectedfrom hens fed a gypsum-augmented diet. The tendency of poultry manure toincrease in pH appears to contribute to a general increase in ammoniaemissions starting in the 24-48 hour period. However, this increase issubstantially lower in manure from hens fed a ration comprising gypsumand zeolite than in manure from hens fed a ration comprising gypsumalone. Clearly, feeds comprising zeolite and an acidogenic substanceacting in concert provide a significant advance in the art, as thiscombination reduces manure ammonia emissions to an unexpected andsignificant extent when compared to industry standard diets or dietsaugmented with just a cation exchanger or just an acidogenic compound.

Additionally, FIG. 2 illustrates the unexpected and beneficial effectson manure ammonia emissions when crude protein levels in feed arereduced in combination with the addition of gypsum/zeolite. Comparisoncalculations in Table 1 indicate a 77% reduction in ammonia emissionsfrom manure produced by chickens fed this reduced protein combinationdiet over the 1-week study period as compared to emissions from manureproduced by chickens fed the control diet.

A comparison of Table 1 data for control diet emissions to low crudeprotein levels/gypsum/zeolite augmented diet emissions indicates a >99%reduction in ammonia emissions in the 0-24 hour period and a 94%reduction in the 24-48 hour period. When those same figures are comparedto the standard crude protein levels/gypsum/zeolite augmented diet, thelow crude protein level/gypsum/zeolite augmented diet has 98% lowerammonia emissions in the first 24-hour period and 82% lower ammoniaemissions in the 24-48 hour period.

As illustrated in FIG. 3, hens fed a ration comprising an appropriatelevel of one or more acidogenic compounds and one or more indigestiblecation exchangers produced manure that off-gassed less ammonia thanmanure produced by animals fed the control rations. Hens fed rationscomprising zeolite, an acidogenic compound, and lower levels ofunabsorbed crude protein produced manure with the lowest level ofammonia emissions.

Experiment 3

Older manure is continually being covered over by fresh as a manure pileaccretes. Because ammonia emission occurs from the surface of themanure, accretion may act to suppress ammonia emissions. If this istrue, then reducing the amount of ammonia off-gassed from fresh manureeven transiently may help to reduce the level of ammonia in a whole henhouse.

In order to test this hypothesis, an entire layer house was fed a rationcomprising 1.25% zeolite with 25% of the supplemental calcium derivedfrom gypsum. A second layer house used as a control was fed a controlration with no zeolite and all of its supplemental calcium derived fromlimestone. Crude protein levels in the two rations were nearlyidentical: 15.3% and 14.8% of total ration weight, respectively.

Because birds in the gypsum/zeolite-amended feed house could likely nottolerate an immediate shift from the standard rations to the amendedrations, birds fed the amended ration were weaned from their standarddiets to the amended rations over a period of about 6 weeks. Testing foraerosol ammonia at the outlets for house air circulation fans was begunas the diet approached the final levels. Readings were taken at 10exhaust fan outlets in each house, and the average values of thosereadings were recorded. Outside temperatures were also recorded todetermine if ammonia emission rates correlated with temperature. Theexperiment was carried out during cold weather when house ventilation iskept at a minimum to conserve heat. During the cold-weather phase of theexperiment, pit fans, which are fans placed in the manure collection pitto circulate air to aid in drying manure, were not in operation. Underthese conditions, the level of ammonia measured at the exhaust fansfairly represents the average ammonia level in the house.

The data from this phase of the test is summarized in Table 6. As thebirds acclimatized to the amended diet, the level of ammonia measured inthe house decreased, with an average reduction of 68% over the term ofthis phase of the study. Near the end of the study, the level of ammoniain the atmosphere of the house correlated well with the level of ammoniaemissions measured from manure samples collected from hens fed similarrations monitored over a 1-week period. Compare, for example, the datain Table 6 with the data in Table 5 and FIG. 4.

As the weather warmed, the pit fans were activated, and ventilationrates increased. Again, ammonia emission readings were obtained at thesame 10 fans used as data points previously. Special attention was paidto insure that the same numbers of ventilation fans were in operation inboth houses during periods of time when data was being collected.Airflow is a significant factor with regard to ammonia emissions. To apoint, increases in airflow cause increases in ammonia emissionsmeasured at the vent fans. As illustrated by the data in Table 7, anincrease in ammonia emissions was noted in both houses as a result ofthe pit fans being placed in operation. However, the levels of aerosolammonia in houses in which the hens were fed a gypsum/zeolite amendedration were significantly lower than the levels measured in the houseswith hens fed the control diet. There was, on average, a 43% reductionin the amount of aerosol ammonia in the houses fed the amended diet overthe houses fed the control diet over the term of this phase of thestudy.

No negative effects on egg production, shell strength, or bird healthwere noted in this whole-house study. In fact, quite the opposite wasnoted. Egg production, shell strength, and bird health were unexpectedlyimproved in birds fed the amended rations over birds fed the industrystandard ration.

Experiment 4

At least some of the ammonia associated with animal manure is derivedfrom the chemical and microbial degradation of amino acids present inthe manure. Reducing the level of crude protein in an animal's rationsmay help to reduce the amount of ammonia produced in the animal's manureby reducing the major source of undigested amino acids in manure:undigested or only partially digested proteins or other polypeptides.

Referring now to Table 5 and FIG. 4, an experiment was carried out todetermine if reducing crude protein levels and increasing the level ofgypsum substituted for limestone in the amended feeds would decrease thelevel of ammonia emitted by birds fed the amended ration. Accordingly,one group of hens was fed a control ration. A second group of hens wasfed a ration comprising gypsum substituted for some of the supplementalcalcium in the ration and lower levels of crude protein than the controlration. The levels of ammonia emitted by manure excreted by these birdswere compared. The control values were measured from manure collectedfrom hens fed the same feed ration as the hens in the control group ofthe whole house study. The 25% gypsum curve shows the effect of theamended diet fed in the whole house study. The 35% gypsum curveillustrates the effect of reducing crude protein from 15.3% by weight ofthe ration to 14.3% by weight as well as increasing the gypsum-basedcalcium replacement levels to 35%. All amended feeds comprised 1.25%zeolite by weight. These data were generated using the same analyticalmethods as previously described.

Referring still to Table 5 and FIG. 4, whole-house ammonia emissions inhouses where hens were fed gypsum/zeolite amended rations wereapproximately 80% less than in the control house. Reducing crude proteinby 1% from 15.3% by weight to 14.3% by weight, and at the same timeincreasing gypsum-based calcium supplementation rates to 35% instead of25%, garners an approximately 95% reduction in ammonia emissions(relative to the control house). That level of reduction wasunexpectedly high. To confirm this, the test was repeated using freshmanure. The reduction in the rate of ammonia production and in the totalamount of ammonia emitted was virtually identical between the twoexperiments.

Moisture levels are known to be a factor affecting ammonia emissions.Therefore, the percentage of solids in each manure sample was alsodetermined. Solids contents in manures generated from consumption ofamended and control rations were very similar, ranging from about 20% to24% for freshly excreted manure.

Experiment 5

High levels of total phosphorus and, especially, high levels of solublephosphates in manure pose significant threats to the environment,particularly when the manure finds its way into the watershed. Thefollowing survey was conducted to determine if addingphosphorus-reactive metals bound to zeolite to an animal's feed rationscould reduce the amount of soluble phosphate in the animal's manure.

Referring now to Tables 2, 3, and 4, manure produced by hens fed rationscomprising zeolite had less soluble phosphorus and less total phosphatethan manure generated by hens fed standard rations, even when the totalamounts of bioavailable phosphorus in each ration were the same. Theobserved drop in the total amount of phosphate in manure produced byhens fed rations comprising 2% by weight of zeolite are illustrated inTable 2. The drop in total phosphate levels observed was unexpected.This reduction in total excreted phosphorus may be due to zeolitespromoting more efficient uptake and utilization of bioavailablephosphorus.

Since soluble phosphorus is environmentally problematic, the ratiobetween soluble and total phosphorus in manure is of interest. Referringnow to data in Table 3, test rations were supplemented with phytase, anenzyme that tends to elevate the amount of bioavailable phosphorus ingrain-rich animal feeds. Additional manure samples were collected, andboth total and soluble phosphorus amounts were determined analytically.These data support the conclusion that feeding zeolites comprisingexchangeable phosphate-reactive cations appears to reduce significantlythe solubility of phosphorus in manure as well as the total amount ofphosphorus excreted.

The zeolite used in this experiment contained exchangeable calcium andmagnesium cations. The reduction in the amount of soluble phosphate maybe due to the formation of insoluble metal phosphate compounds.

In another aspect of the invention, synthetic zeolites can be doped withcalcium and magnesium before the zeolite is added to animal feeds.Zeolite dosed with a metal such as calcium and/or magnesium will help toreduce the amount of soluble phosphate in manure produced by animals feda diet comprising the zeolite.

Tests were conducted on full size layer houses to determine if theamended rations of the present invention lowered the soluble phosphatelevels in manure produced under production conditions. Hens in one housewere fed a control ration while hens in a second house with conditionsidentical to the first house were fed the amended rations used for thelarge-scale study. Samples of manures of similar age were removed fromthe manure collection areas of the two layer houses. Samples wereanalyzed for total Kjeldahl nitrogen, ammonia, and total/solublephosphorus. All results were reported on a dry weight basis, and thesedata are summarized in Table 4. Manure from birds fed agypsum/zeolite-amended diet contained 5.58% nitrogen, 0.93% ammonia,0.97% total phosphorus, and 0.14% soluble phosphorus. Manure from birdsfed the control (industry standard) ration contained 4.88% nitrogen,1.94% ammonia, 1.08% total phosphorus, and 0.30% soluble phosphorus.

Experiment 6

It is another aspect of the invention to produce manure that is bettersuited for use as a component of fertilizer than is manure produced byanimals fed standard rations. Plants require both nitrogen andphosphorus; however, too much of either element can adversely affectplant health. The ratio of nitrogen to phosphate (N:P ratio) of manureproduced by hens fed standard rations is oftentimes so low that thismanure must be processed before it can be used to produce fertilizer.This processing adds to the expense of fertilizer made from such manure.Manure produced by hens fed the amended feed of the present inventionhad an unexpectedly more favorable N:P ratio.

In order to determine if the combination of feeding hens a cationexchanger, an acidogenic compound, and one or more phosphate-reactivemetals would have an impact on the manure's N:P ratio, hens were fed thevarious rations. The nitrogen/phosphorus (N:P) ratio of manure frombirds fed the amended ration is 5.8:1, whereas manure from control birdsexhibited an N:P ratio of 4.5:1. The N:P ratio of manure produced usingthe rations of the present invention is better suited for use in plantfertilizer than is manure produced by animals fed the control ration. Itis also worth noting that the reduction in ammonia levels in manure frombirds fed amended feed is roughly consistent with the previously statedreductions in aerosol ammonia levels observed in the large-scale studyreported in Experiment 4.

Manure from hens fed the amended ration has a lower level of solublephosphate than manure from hens fed the control ration. Given thatsoluble phosphate in surface water can be a significant environmentalproblem, manure produced by animals fed rations comprisinggypsum/zeolite amended feed makes for more environmentally friendlymanure. When the manure generated from consumption of the amended feedgets applied to a field, there is less phosphorus that can dissolve inrain and run off to the local streams and ponds.

Experiment 7

Still another aspect of the invention is a method of reducing the numberof flies associated with manure produced by animals fed the inventiverations. This unexpected benefit was first observed in the whole-housetrial. Referring now to Table 8 and FIG. 5, fly card data were collectedover a 1-week period. Data were collected from whole houses in whichhens were fed either the control (conventional industry standard diet)or one of the amended diets. One amended diet included, a zeolite and25% gypsum, and the other amended diet included zeolite, 35% gypsum, andreduced crude protein levels (crude protein levels were reduced by 1%).These feeding experiments were carried out in duplicate.

As illustrated by the data in Table 8 and FIG. 5, there are fewer fliesin houses in which hens were fed the gypsum/zeolite amended ration thanin houses in which hens were fed the control ration. A similar reductionwas also observed at the manure storage pit level and at the bird cagelevel. Additionally, noticeably fewer maggots and flies were present inthe house in which the amended feeds were utilized. This effect may bebased on acidification of the manure, as many types of fly larvae arenot tolerant of a growth medium with a pH below 7 SU. TABLE 1 AmmoniaEmission Control Feed Amendments Gypsum/ Gypsum/ Zeolite Zeolite ControlZeolite Gypsum Std CP Reduced CP Day 1 288 144 69.5 42.8 0.99 Day 2 235398 178 73 13.1 Day 3 57.9 107 142 90.6 50 Day 4 13.8 22.4 76.3 62 50Day 5 4.9 6 26.9 30.4 17 Day 6 2.12 3.95 13.2 15.4 6.68 Day 7 1.67 2.816.59 4.4 2.8 Totals 603.39 684.16 512.49 318.6 140.57 % Reduction 0.00−13.39 15.06 47.20 76.70

TABLE 2 Effects of zeolite on total phosphorus excreted, shown in unitsof lbs./ton of manure Supplemented with % Reduction in zeolite ControlDiet Phosphate Sample 1 29.54 39.28 24.80 Sample 2 32.66 40.64 19.64Sample 3 28.9 29.68 2.63 Sample 4 17.42 24.4 28.61 Sample 5 26.58 33.8421.45 Sample 6 13 19.58 33.61 Sample 7 12.46 19.88 37.32 Sample 8 10.520.06 47.66

TABLE 3 Effects of Zeolite on Soluble/Total Phosphorus Ratio. ZeoliteControl % Reduction (ppm) (ppm) in Soluble Phosphate Soluble Phosphorus207 2760 92.50 Total Phosphorus 1380 3900 64.62 % Soluble Phosphorus15.00 70.77

TABLE 4 Manure Analysis, results reported on a dry weight basis.Supplemented Unsupplemented feed feed (ppm) (ppm) Total KjeldahlNitrogen 55700 48800 Ammonia 9290 19400 Total Phosphorus 9670 10800Soluble Phosphorus 1360 3000

TABLE 5 Results of dose response/optimization study. 35% Gypsum 35%Gypsum 25% CP reduced by CP reduced by Control Gypsum 1% Trial 1. 1%Trial 2. Day 1 112 32.2 1.69 4.96 Day 2 185 31.6 1.47 0.79 Day 3 64.16.6 10.8 1.89 Day 4 7.96 1.55 2.06 2.36 Day 5 2.2 0.76 1.15 1.79 Day 61.56 1.15 1.14 1.87 Day 7 1.32 1.12 1.29 1.80 Total 374.14 74.98 19.615.46 % Reduction 0.00 79.96 94.76 95.87

TABLE 6 Averaged Ammonia Emissions at Exhaust Fan Inlets Measured Whenthe Pit Fan Ventilation Fans Were Inactivated. Outside Date Amended FeedControl % Reduction Temperature Day 1 18.0 41.6 56.7 38 Day 2 17.2 45.562.2 23 Day 3 15.7 40.0 60.8 28 Day 4 15.0 43.1 65.2 36 Day 5 14.8 35.057.7 20 Day 6 14.5 36.4 60.2 16 Day 7 18.0 39.6 54.5 12 Day 8 16.9 37.054.3 2 Day 9 11.5 42.7 73.1 24 Day 10 12.8 45.4 71.8 34 Day 11 12.0 48.875.4 34 Day 12 12.0 53.0 77.4 37 Day 13 8.6 48.8 82.4 46 Day 14 8.3 43.380.8 38 Day 15 5.9 41.1 85.6 48

TABLE 7 Averaged Ammonia Emissions at Exhaust Fan Inlets Measured Whenthe Pit Fan Ventilation Fans Were Activated. Outside Date Amended FeedControl % Reduction Temperature Day 1 37.7 56.1 32.8 48 Day 2 34.8 57.339.3 48 Day 3 27.6 50 44.8 49 Day 4 12.1 30.7 60.6 56 Day 5 30.6 42 27.162 Day 6 23.1 36.1 36.0 50 Day 7 22.5 40.9 45.0 54 Day 8 21.4 45.9 53.447 Day 9 16.2 27.9 41.9 57 Day 10 21.1 38.9 45.8 42

TABLE 8 Fly Count Data: Gypsum/Zeolite Amended Feed vs. ConventionalIndustry Standard Diet. Amended Feed Control Week 1 1.2 1.2 Week 2 1.81.6 Week 3 1.8 1.4 Week 4 1.8 2.2 Week 5 1.8 1.8 Week 6 1.8 2.2 Week 71.8 2.6 Week 8 1.8 2 Week 9 1.6 2 Week 10 1.8 2.2 Week 11 1.2 2.8 Week12 1.4 2.4 Week 13 1.2 2.8 Week 14 1.6 2.8 Week 15 1.4 3 Week 16 1.8 3.2

While the invention has been illustrated and described in detail in thefigures and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected. As well, while the invention wasillustrated using specific examples, theoretical arguments, accounts,and illustrations, these illustrations and the accompanying discussionshould by no means be interpreted as limiting the invention. Allpatents, patent applications, and references to texts, scientifictreatises, publications, and the like referenced in this application areincorporated herein by reference in their entirety.

1. An animal feed comprising: an acidogenic composition and a cationexchanger, wherein said acidogenic composition is a fermentable fiber,said fermentable fiber promotes the formation of ammonium cations inwaste material produced by an animal provided said feed, and saidammonium cations bind to said cation exchanger.
 2. The animal feed ofclaim 1, wherein said fermentable fiber is selected from the groupconsisting of cellulose, soybean hulls, distiller's dried grains withsolubles, distiller's dried grains without solubles, wet distiller'sgrains with solubles, wet distiller's grains without solubles, sugarbeet pulp, wheat middlings, and a combination thereof.
 3. The animalfeed of claim 1, wherein said cation exchanger includes diatomaceousearth.
 4. The animal feed of claim 3, wherein said diatomaceous earth isCelite® diatomaceous earth.
 5. An animal feed comprising: an acidogeniccomposition; a cation exchanger: and a source of crude protein, whereinsaid acidogenic composition promotes the formation of ammonium cationsin waste material produced by an animal provided said feed, saidammonium cations bind to said cation exchanger, and said source of crudeprotein contains a limiting amount of at least one amino acid.
 6. Theanimal feed of claim 5, further including an amino acid supplementhaving at least one amino acid selected from the group consisting oflysine, methionine, threonine, and tryptophan.
 7. The animal feed ofclaim 6, wherein said fermentable fiber is a source of said amino acidselected.
 8. The animal feed of claim 6, wherein said fermentable fiberis selected from the group consisting of soybean hulls, distiller'sdried grains with solubles, distiller's dried grains without solubles,wet distiller's grains with solubles, wet distiller's grains withoutsolubles, sugar beet pulp, wheat middlings, and a combination thereof.9. The animal feed of claim 6, wherein said cation exchanger includesdiatomaceous earth.
 10. The animal feed of claim 9, wherein saiddiatomaceous earth is Celite® diatomaceous earth.
 11. A method forreducing the level of ammonia aerosol from manure having a pH andcontaining ammonia, the method comprising the steps of: providing ananimal feed including, a cation exchanger capable of binding ammoniumcations, and an acidogenic composition wherein said acidogeniccomposition is a fermentable fiber, and feeding said animal said feed,wherein said feeding reduces said pH of said manure produced by saidanimal and causes at least a portion of said ammonia to protonateproducing said ammonium cations.
 12. The method of claim 11, whereinsaid cation exchanger retains said ammonium cation binding capabilityafter passage through a digestive tract of said animal.
 13. The methodof claim 12, wherein said feeding includes feeding said feed to saidanimal selected from the group consisting of a pig, a sheep, a cow, achicken, a duck, a turkey and a goose.
 14. The method of claim 11,wherein said providing includes providing said animal feed including afermentable fiber selected from the group consisting of cellulose,soybean hulls, distiller's dried grains with solubles, distiller's driedgrains without solubles, wet distiller's grains with solubles, wetdistiller's grains without solubles, sugar beet pulp, wheat middlings,and a combination thereof.
 15. The method of claim 11, wherein saidproviding said animal feed including said cation exchanger includesproviding diatomaceous earth.
 16. The method of claim 15, wherein saidproviding said animal feed including said cation exchanger includesproviding Celite® diatomaceous earth.
 17. The method of claim 11,wherein said providing said animal feed further includes providing asource of crude protein having a level, wherein said crude protein islimiting in at least one amino acid.
 18. The method of claim 17, whereinsaid providing said animal feed further includes providing said feedcontaining an amino acid supplement, having at least one amino acidselected from the group consisting of lysine, methionine, threonine, andtryptophan.
 19. The method of claim 18, wherein said amino acid selectedis contained in said fermentable fiber included in said animal feed andsaid fermentable fiber is selected from the group consisting of soybeanhulls, distiller's dried grains with solubles, distiller's dried grainswithout solubles, wet distiller's grains with solubles, wet distiller'sgrains without solubles, sugar beet pulp, wheat middlings, and acombination thereof.
 20. The method of claim 19, wherein said providingsaid animal feed including said cation exchanger includes providingdiatomaceous earth.
 21. The method of claim 20, wherein said providingsaid animal feed including said cation exchanger includes providingCelite® diatomaceous earth.